Builders working in an old pub in the Irish Republic have unearthed one of the most significant finds of gold coins ever recorded in the country.

Eighty-one coins, mostly guineas and half guineas dating back to the 17th century, were dug up from clay underneath floorboards in the fire-damaged premises of Cooney's pub in the town of Carrick-on-Suir, County Tipperary.

Marie McMahon, the curator at South Tipperary Museum in Clonmel where the coins were first stored said: "We were told that they were gold and you never really believe it, normally you would find silver, but they were in fantastic condition.

"There are one or two coins buckled and one tarnished, but overall fantastic condition. They'd be incredibly valuable but legally we would not be allowed to discuss that."

Experts at the National Museum of Ireland, which is putting the coins on show for the first time on Wednesday, described the find as the most important in decades.

"No comparable 17th century hoard of gold coins has been found in Ireland since the discovery in Portarlington, County Laois, around 1947, of a hoard that contained little over 100 gold coins as well as some silver coins," a spokeswoman said.

The collection depicts the reigns of Charles II, James II and William and Mary, who are featured in a joint portrait.

The National Museum said that it appeared that the coins had been hidden "in a line together".

It is believed they may have originally been wrapped and held together by material which has disintegrated over time.

Ms McMahon said she suspects the coins may have belonged to a merchant as the town was a trading centre in the 17th century - old maps are to be checked, to try to find out what was previously on the site.

The coins are mainly guineas, with a small number of half guineas, the name given to a British gold coin made by the Royal Mint between 1663 and 1814.

They were called guineas because the gold used in making some of them came from West Africa.

More research is being carried out into the coins and their historical background.